The invention relates to thermal interface materials and their use.
In the computer industry, there is a continual movement to higher computing power and speed. Microprocessors are being made with smaller and smaller feature sizes to increase calculation speeds. Consequently, power flux is increased and more heat is generated per unit area of the microprocessor. As the heat output of the microprocessors increases, heat or “thermal management” becomes more of a challenge.
One aspect of thermal management is known in the industry as a “thermal interface material” or “TIM” whereby such a material is placed between a heat source, such as a microprocessor, and a heat dissipation device to facilitate the heat transfer. Such TIMs may be in the form of a grease or a sheet-like material. These thermal interface materials also are used to eliminate any insulating air between the microprocessor and heat dissipation device.
TIMs typically are used to thermally connect a heat source to a heat spreader, that is, a thermally conductive plate larger than the heat source, in which case they are referred to as TIM Is. TIMs may also be employed between a heat spreader and a thermal dissipation device such as a cooling device or a finned heat sink in which case such TIMs are referred to as TIM IIs. TIMs may be present in one or both locations in a particular installation. SUMMARY
In one embodiment, the invention provides a thermally conductive grease that comprises 0 to about 49.5 weight percent of carrier oil, about 0.5 to about 25 weight percent of at least one dispersant, and at least about 50 weight percent of thermally conductive particles. The thermally conductive particles comprise a mixture of at least three distributions of thermally conductive particles, each of the at least three distributions of thermally conductive particles having an average (D50) particle size which differs from the other distributions by at least a factor of 5.
In another embodiment, the invention provides a method of making a thermally conductive grease of the invention that comprises the steps of providing carrier oil, dispersant, and thermally conductive particles, and then mixing the carrier oil (if present), dispersant, and thermally conductive particles together.
In one aspect, the carrier oil (if present) and dispersant are mixed together, and the thermally conductive particles are mixed sequentially, finest to largest average particle size into the carrier oil and dispersant mixture. In another aspect, the thermally conductive particles are mixed together, and then mixed into the carrier oil (if present) and dispersant mixture. In another aspect, a portion or all of the thermally conductive particles are pre-dispersed with a dispersant prior to mixing the thermally conductive particles into the carrier oil (if present) and dispersant mixture.
In another embodiment, the invention provides a microelectronic package comprising a substrate, at least one microelectronic heat source attached to the substrate, and a thermally conductive grease disclosed in this application on the at least one microelectronic heat source.
In one aspect, the invention provides the above microelectronic package further comprising a heat spreader and thermally conductive grease disclosed in this application between the microelectronic heat source and the heat spreader.
In another aspect, the invention provides a microelectronic package comprising a substrate, at least one microelectronic heat source attached to the substrate, a heat spreader, and a heat dissipation device attached to the heat spreader wherein a thermally conductive grease disclosed in this application is between the heat spreader and the heat dissipation device.
In another aspect, the invention provides a microelectronic package comprising a substrate, at least one microelectronic heat source attached to the substrate, a heat spreader, a thermally conductive grease disclosed in this application between the microelectronic heat source and the heat spreader and a heat dissipation device wherein thermally conductive grease is between the heat spreader and the heat dissipation device.